Friday, February 7, 2025

SLI Service Level Indicator Examples, Types And Importance

What is a Service Level Indicator?

The performance and availability of a service or distributed system are gauged by measurable, established criteria known as service level indicators, or SLIs. Latency, error rate, throughput, availability, uptime, and reaction time are a few of these measures. The fact that SLI indicators are collected and presented as rate, average, percentage, or percentile should not be overlooked. A 99.99% availability, for instance, might be considered a SLI for availability.

Why Are SLI Service Level Indicator Important?

Organisations can quantitatively and impartially assess the availability and performance of their services in relation to the business objectives by using SLIs. As nice as that sounds, SLI Service Level Indicator provide organisations with much more.

SLIs are significant for the following reasons:

  • SLI offers a particular method for establishing clear objectives and standards for your service. You can guarantee that you fulfil your end users’ expectations, adhere to your service-level agreement (SLA), and stay out of trouble by restricting the SLI to the metrics that accurately represent your service.
  • DevOps and Site Reliability Engineers (SRE) may detect problems early by keeping an eye on SLI Service Level Indicator since it makes it easier to determine what is wrong. It also aids in the prompt and proactive resolution of the aforementioned problem.
  • Better service quality results from problems being identified and fixed. Finding problems enables the team to monitor the progress of your user journey, gauge customer happiness, enhance user experience, and guarantee company success.
  • SLI may also be used to monitor your services’ availability and performance over time. One can make more proactive progress towards corporate objectives with this knowledge.

SLIs, SLOs, and SLAs

Three phrases that are commonly used while discussing service-level management are service-level indicator (SLI), service-level objective (SLO), and service-level agreement (SLA). Despite their similar sounds, these three phrases are actually quite distinct.

As previously stated, SLIs are quantifiable measures used to monitor service availability and performance. As a result, they serve as the cornerstones and will be employed to ascertain whether the organization’s service goals are fulfilled.

SLOs are the objective that the organisation has set in order to quantify the level of service quality that the service provider hopes to attain for a certain SLI. Use these as benchmarks to assess your SLI performance.

The customer and service provider agree on SLA terms. It describes the service required, what is acceptable, and the penalties of not meeting it. It is crucial to understand that SLOs in SLAs are subject to change and should be examined on a regular basis.

Let’s look at an illustration.

Supposing you decide to evaluate the security of your API using authentication failures as metrics. Here, the SLI Service Level Indicator is an authentication failure. Contextually speaking, authentication failures are just the frequency of authentication failures; as such, they are a strong predictor of possible unauthorised access.

You set a goal of 1% to make sure the API is reliable and safe.

You engage into an agreement with this B2B customer and guarantee that your API has an authentication failure rate of 1.2% in order to ensure that you can deliver to your client. The SLA is the document that describes the details of this agreement between you and the client.

SLAs are the legally established term of engagement, SLOs are your standard or aim for each SLI, and SLIs are the quantifiable measurements.

Types of Service Level Indicators

Request-based and window-based SLIs are the two basic varieties.

Request-based SLIs

The ratio of completed requests or transactions made in or to service to the total number of requests or transactions is measured by request-based SLIs. The service provider can identify performance problems or obstacles to fulfilling consumer requests with the use of this measure.

Therefore, the following will be the formula for request-based SLI:

Request-oriented Good requests divided by all requests is SLI Service Level Indicator.

Assume that a service receives around 20,000 queries in total. Just 17,000 of these petitions were fulfilled or successful. The service has an 85% success rate as a result.

It is important to understand that in order to evaluate and assess request-based SLIs over time, they must be monitored within a certain time period.

Window-based SLIs

Window-based SLIs evaluate a service’s availability and performance across a predetermined period of time. A window period is used to compute the number of successful requests. Within a certain time period or during crucial hours, this SLI assists in monitoring, elevating, and identifying trends in the service.

The following will be the formula for window-based SLI:

Window-based SLI = good periods / total Periods

Therefore, a service has a 90% success rate during peak hours (2:00 pm to 6:00 pm) if 540,0000 of the 600,000 requests are successful.

Service Level Indicator examples

SLIs are metrics used to monitor a service or system’s performance, commonly in service level agreements. Some examples:

Response Time

The average response time to user enquiries. SLIs can measure webpage load times.

Availability/Uptime

The proportion of service uptime. An SLI for a cloud service may track its 99.9% availability.

Error Rate

Error proportion of requests. A website’s SLI may count failed transactions or broken links.

Latency

The time between request and answer. Consider how long a server takes to react to a user inquiry.

Throughput

The amount of data a system processes periodically. Example: e-commerce platform transactions per minute.

These indicators help organisations monitor and sustain service quality.

Challenges of SLI Service Level Indicator

It might be difficult to measure service availability and performance for a number of reasons. Here are a few:

  • SLI needs to support the user experience journey, be measurable, and be in line with corporate goals. To do this, one needs to comprehend the elements of the service and connect with people.
  • SLI Service Level Indicator data collection and processing may be a difficult and resource-intensive operation. The procedure need a dependable infrastructure for data gathering and processing in order to ensure data consistency and quality.
  • When there are several SLIs or when SLIs are coupled, it becomes difficult to interpret SLI Service Level Indicator data. You must link and integrate data from several sources in order to comprehend your metrics, and you must use the results to spot trends and problems.
  • Setting that appropriately represent the service while juggling the demands and expectations of each SLI’s users is necessary for SLO definition. This may affect the company’s goals and result in extra expenses.
Thota nithya
Thota nithya
Thota Nithya has been writing Cloud Computing articles for govindhtech from APR 2023. She was a science graduate. She was an enthusiast of cloud computing.
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